In the conventional rheology field, a rheometer is used to measure the deformation and flow behavior of a fluid when a stress is imposed thereon. The rheometer measures global Theological characteristics of the specimen of the fluid subjected to a stress set by the rheometer, the global rheological characteristics corresponding to data averaged over the volume of the specimen. These global rheological characteristics are relevant for fluids that undergo homogeneous deformations throughout the stressed specimen. The rheometer therefore proves to be an effective tool for studying fluids under what is called homogeneous flow, that is to say fluids whose rheological behavior is identical throughout the specimen.
However, it proves to be an incomplete tool for characterizing fluids whose rheological behavior is more complex, namely stressed fluids undergoing inhomogeneous local deformations, such as slip at the walls, local fractures, shear bands, etc.
Now, these complex fluids play a very important role in many industrial fields, such as in the food, chemical and cosmetics industries. Their study is therefore of great industrial importance.